A spaceborne microorganism that feeds on starship hull metal, found on both the Enterprise-D and the Klingon cruiser Pagh during an officer exchange.
Subatomic bacteria are microscopic spaceborne organisms that consume the alloys of a starship's hull, doubling in number at short intervals until the plating begins to fail.
They appear in A Matter of Honor. The Benzite exchange officer Mendon notices a patch on the hull of the Klingon ship Pagh while Riker is transferring aboard as its first officer, but following the custom of his people says nothing until he has a full analysis. By then the same growth is on the Enterprise-D.
Aboard the Pagh, Captain Kargan concludes that the Federation has attacked his ship with a secret weapon and prepares to open fire. Riker has to outmanoeuvre him and take command so that the Enterprise can supply the simple treatment that removes the organism.